AB1037 CRYSTAL DEPOSITS IN PRIMARY SYNOVIAL CHONDROMATOSIS
Authors: M. Bély, Á. Apáthy
Journal: Annals of the Rheumatic Diseases (2022)

Background Primary synovial chondromatosis ( prSynCh ) is a metaplastic disorder of the synovial membrane, characterized by chondrocyte differentiation of synovial pluripotent stem cells, and chondroid tissue production. The prSynCh may be accompanied with amorphous calcium phosphate or carbonate deposition and bone formation, with or without true medullary spaces. The cause of stem cell differentiation is unknown; different irritative agents (infective, toxic, mechanic, etc.) are mentioned, but the condition may occur spontaneously as well [1, 2]. Crystal deposits as irritative agents of primary synovial chondromatosis due to a clinically latent metabolic disorder are not mentioned. Objectives The aim of this study was to determine the formal pathogenesis of synovial chondromatosis, and to detect crystal deposits in synovial membrane in order to explore the possible role of metabolic diseases in transformation of stem cells into chondrocytes, i.e., to demonstrate the metabolic origin of prSynCh . Methods Surgical specimens (synovial membranes of 14 knees, 4 hips and 2 elbows) of 20 patients (females 13. mean age of 50.17 years, range 40 – 74; males 7, mean age of 40.64 years, range 30 – 76years) with primary synovial chondromatosis were studied histologically. Cases of secondary synovial chondromatosis, i.e., due to osteoarthritis, rheumatoid arthritis, aseptic (avascular) bone necrosis, osteochondral traumatic injury, etc. were excluded. Serial sections (5 microns) of tissue samples were stained with H-E , Alizarin red S (specific for calcium), and von Kossa ’s reaction (specific for phosphate and/or carbonate), and were compared with unstained sections according to Bély and Apáthy (2013). The non-staining technique is a very sensitive method to detect small crystals with weak birefringence viewed under polarized light [3-5]. Results Chondromatosis (chondroid formation without osteoid or bone formation) was found in 8 , osteochondromatosis (chondroid with osteoid and bone formation) in 11 , and only bone formation in 1 of 20 patients. True medullary spaces accompanied bone formation in 8 of 12 cases. Different stages of chondroid and/or bone formation existed side by side in the same histologic section. In non-stained sections HA [Ca 5 (PO 4 ) 3 (OH)], CPPD [Ca 2 P 2 O 7 .2H 2 O] crystals, and/or unidentified crystal fragments were detected in all cases. Amorphous calcium phosphate and/or carbonate deposits were present in 12 of 20 patients. Conclusion The formal pathogenesis of primary synovial chondromatosis corresponded to the descriptions of the pertinent literature characterized by clean chondromatosis, mixed osteochondromatosis, and pure osteomatosis. We assume that the pre chondromatous phase of prSynCh starts with hydroxyapatite ( HA ) crystal deposition with or without calcium pyrophosphate dihydrate ( CPPD ) deposits, and the prSynCh may be regarded essentially a metabolic disease, like chondrocalcinosis or apatite rheumatism. The difference between these diseases is only in the prevalence and amount of HA and/or CPPD crystals, accompanied with or without amorphous calcium phosphate and/or carbonate deposits. In our opinion the chondrocalcinosis, apatite rheumatisms and prSynCh represent the same group of metabolic diseases. References [1]“Synovial Chondromatosis - OrthoInfo – AAOS, https://orthoinfo.aaos.org/en/diseases--conditions/synovial-chondromatosis [2]Synovial Chondromatosis – GARD, https://rarediseases.info.nih.gov/diseases/6054/synovial-chondromatosis [3] Bély M, Apáthy Á : Structural Chemistry &amp; Crystallography Communication, 2016; 2 (1:15): 1-6. http://structural-crystallography.imedpub.com/archive.php [4] Bély M, Apáthy A : Clinical Archives of Bone and Joint Diseases, 2018; 1.2 DOI: 10.23937/cabjd-2017/1710007 [5] Bély M, Apáthy A : “Crystal deposits in tissue of patients with chondrocalcinosis and apatite rheumatism – Microscopic identification of CPPD and HA with the non-staining technique of Bely and Apáthy”. BAOJ Clinical Trials, 4: 018. Disclosure of Interests None declared